Method of making dental restorations and pontic member therefor

ABSTRACT

A pontic has a rigid core and a detachable flexible plastic cap of 1 to 2.5 mm wall thickness having the external contour of a tooth. The core extends laterally slightly above the gum line to either side and has an exposed, flat, vertical face which may be secured to a matching face of an adjacent pontic or to a similar face of an insert attached to a wax or plastic coping or a wax or plastic crown which is, in turn, attached to the abutment die. In use, the abutments in a die are waxed in crowns, or copings, as per ordinary practice except for the above-mentioned inserts fixed to the abutment coping or crowns. Carding wax is applied to the tissue area of the model, and the pontics with caps in place are stuck to the wax, forming an indentation, matrix or index. Articulation is checked. The faces of the lateral extensions of the pontic cores are cemented to the adjacent abutment inserts or crown or copings extensions. Caps are then removed. The cores and abutment inserts are then invested as per the lost wax technique and metal cast into the mould cavity of the investment, also as per lost wax technique. The metal is porcelainized as in ordinary practice.

United States Patent 1 Millet METHOD OF MAKING DENTAL RESTORATIONS ANDPONTIC MEMBER THEREFOR [76] Inventor: William G. Millet, 2031 Lone OakAve., Napa, Calif. 94558 [22] Filed: Mar. 2, 1972 [21] Appl. No.:231,138

Primary Examiner -Robert Peshock Attorney, Agent, or Firm-Julian CaplanABSTRACT A pontic has a rigid core and a detachable flexible [45] May 7,1974' plastic cap of 1 to 2.5 mm wall thickness having the externalcontour of a tooth. The core extends laterally slightly above the gumline to either side and has an exposed, flat, vertical face which may besecured to a matching face of an adjacent pontic or to a similar face ofan insert attached to a wax or plastic coping or a wax or plastic crownwhich is,'in turn, attached to the abutment die. In use, the abutmentsin a die are waxed in crowns, or copings, as per ordinary practiceexcept for the above-mentioned inserts fixed to the abutment coping orcrowns. Carding wax is applied to the tissue area of the model, and thepontics with caps in place are stuck to the wax, forming an indentation,

matrix or index. Articulation is checked. The faces of the lateralextensions of the pontic cores are cemented to the adjacent abutmentinserts or crown or copings extensions. Caps are then removed. The coresand abutment inserts are then invested as per the lost wax technique andmetal cast into the mould cavity of the investment, also as per lost waxtechnique. The metal is porcelainized as in ordinary practice.

6 Claims, 17 Drawing Figures PATENTEDIAY 11914 SHEET 1 [IF 2 1 Fig.

PATENTED MAY 7 I874 SHEET 2 BF 2 Fi 15 Fig. 15

1 METHOD OF MAKING DENTAL RESTORATIONS AND PONTIC MEMBER THEREFOR Thisinvention relates to a method of making dental restorations and also toa pontic member used in practicing the method. It is a principal objectof the present invention to provide pontic members formed of a hard coreof the shape which the metal part of the restoration occupies; andfurther, provided with a cap of a softer and more flexible plastic whichacts as a guide when positioning the pontic and which represents theporcelain which is subsequently applied to the metal. The flexible capis removable from the hard core.

In accordance with conventional practice, a considerable amount of timeis required in applying wax to a pontic so that the waxed pontic has areduced shape as compared with the completed tooth in the restoration.The present invention eliminates the need of waxing the reduced ponticand this greatly reduces the time required in making the model for themetal casting.

Another advantage of the invention is the fact that waxing of thereduced pontics is a technique which requires skill. Since the operationis eliminated in accordance with the present invention, the requiredskill of the technician is greatly reduced, and since the time is alsoreduced, the cost of, preparing the model for investment iscorrespondingly reduced.

Still another advantage of the invention is the fact that the removableplastic caps are of uniform thickness and represent by thatthickness'the recommended correct thickness 'of the porcelain which issubsequently applied to the metal frame. Many of the failures inproducing adequate restorations are attributable to the fact that thetechnician-applying the porcelain does not understand, the intention ofthe technician preparing the model for investment and the thickness ofthe porcelain is not applied properly. The present invention eliminatesthe likelihood of such confusion.

Other objects of the present invention will become more apparent uponreading the following specification and referring to the accompanyingdrawings in which similar characters of reference representcorresponding parts in each of the several views.

In the drawings:

FIG. 1 is a top, or occlusal, plan of a molar pontic in accordance withthe present invention.

FIG. 2 is a vertical sectional view taken substantially along the line2-2 of FIG. 1. I

FIG. 3 is a side elevational view of anincisor pontic in accordance withthe present invention.

FIG. 4 is a front elevational view of the pontic of FIG. 3 viewed fromthe lingual side. I

FIG. 5 is a schematic elevational view from the lingual side of a diefor a bridge restoration showing preliminary steps in the formation ofthe practice of the method of the present invention.

FIG. 6 is a view similar to FIG. 5 showing the addition of four ponticsin accordance with the present invention to the abutments of FIG. 5.

FIG. 7 is a fragmentary view of the structure of FIG. 6 showingcementing of the pontics to an abutment and also to each other.

FIG. 8 shows the removal of the caps from the pontics and the attachmentof sprue formers to the structure of FIG. 7.

2 FIG. 9 shows an investment made from the model of FIG. 8.

FIG. 10 shows the metal casting made'from the investment of FIG. 9 whilestill in the investment.

5 FIG. 11 is a rear elevational view showing a restoration formed inaccordance with the present invention viewed from the lingual side.

FIG. 12 is an enlarged sectional view through one of the teeth of FIG.11 take substantially along the line 12-12 of FIG. 11.

FIG. 13 is a view similar to FIG. 2 of a modification.

FIG. 14 is an elevational view from the lingual side showing amodification of the structure of FIG. 2.

FIG. 15 is a sectional view taken substantially along line 15'l5 of FIG.14.

FIG. 16 is a view similar to FIG. 3 of a modification.

FIG. 17 is a view similar to FIG. 4 of the modification of FIG. 16.

Pontics in accordance with the present invention are shown in FIGS. 1-4inclusive. The pontic 21 of FIGS. 1 and 2 is for a molar and the pontic21a of FIGS. 3 and 4 for an incisor, but the present invention isadaptable to the various positions in the dental art. In the center ofthe pontic 21 or 21a is a core 22 formed of a plastic material such asan acrylic, lucite, plexiglass or some other hard material. Generallyspeaking, the size of core 22 is such that there is a wall thickness of1 to 2.5 mm between the core and the outline of the tooth which the corerepresents. The exceptions to this wall thickness are the for'mation'ofa lingual extension 23 extending immediately above the gum line and intoproximal lateral extensions 24 on either side. The extensions 23, 24represent in'practical effect the exposure of metal in the completedrestoration, and the difference between the exterior of the core 22 andthe ultimate wall thickness of the tooth represents the porcelain whichis applied to the metal portion of the restoration after casting. Eachlateral extension 24 is formed with an exposed,'vertical, flat face 26for the purpose of attachment of thepontic to adjacent pontics orabutments as hereinafter explained. Where the core 22 joins theextensions 23, 24 there are chamfers 27 to provide a smooth transitionbetween the metal and the porcelain which is later applied.

Fitting tightly on core 22 but removable therefrom is cap 31 which ispreferably formed of a flexible plastic such as polyethylene and hasfour desirable characteristics. One is that it is readily removable fromthe core when necessary in the performance of the method; second, itdoes not readily adhere to cement. The third characteristic is that cap31 acts as a guide with which to correctly position the cores on thedental arch. The fourth characteristic is that the wall thickness of cap31 correctly represents the thickness of porcelain which is eventuallyapplied to the metal casting. The crown 32 of the pontic 21 of FIGS. 1and 2 has the exterior configuration of a molar (but see FIG. 13),whereas the crown 32a of pontic 21a of FIGS. 3 and 4 has the straightedge of an incisor. For other teeth, the crown 32 has a correspondingproper external shape. The labial surface33 of the cap extends down tothe bottom of the pontic, whereas the lingual surface 34a extends downonly to the upper edge of lingual extension 23 of core 22. The wallthickness of the cap 32, as has previously been mentioned, is quite thinbeing about I to 2.5

mm. The pontic 21 or 210 is manufactured in various shapes dependingupon the location of the tooth. In addition to these fundamental shapes,the pontics are provided in different widths and in different lengths toaccommodate the natural tooth size of the patient. The mesial, distaland bottom, or tissue bearing, surfaces can be relieved or ground awayto slightly alter the shape of the pontic, as is standard procedure whenassembling artificial teeth. In forming the restoration, the technicianselects the appropriate width and length of pontics which conform to theshape of the natural teeth of the patient.

In the practice of the invention, the dentist prepares abutment teeth inthe mouth of the patient by reduction in accordance with conventionalpractice. An impression of at least one jaw is made using standardimpression materials. Usually both the upper and lower jaw impressionsare obtained. The correct bite is established by the use of a wax sheet.Thus from the standpoint of the dentist, practice of the presentinvention requires no alteration of conventional practices, and thedentist himself need acquire no new techniques.

At the laboratory, the first step is to cast stone (plaster) models fromthe impressions provided by the dentist, and these models arearticulated in a standard articulator. The particular area where therestoration is to be constructed is then sliced from one of the modelsto form a model or cast 36 in accordance with standard techniques.

A model or cast 36 usually has two abutment dies 37 (see FIG. whichcorrespond to the reduced abutment teeth left in the mouth by thedentist and these abutment dies are detachable from the model. Thetechnician then applies wax. The crown or coping 38 corresponds to theshape of the abutment tooth which has been reduced by the dentist at thetime that the impression was made of the patients mouth. The crown orcoping 38 will ultimately in the metal portion of the restorationcomprise a socket or coping which fits over the abutment tooth in themouth of the patient. The technician applies to the identulous side ofthe crown or coping 38 at the gum line an insert of the same type ofplastic as is used for the core 22, and this insert 39 has an exposed,vertical flat face 41 corresponding in shape to the flat face 26 andlocated so that when a pontic 21 is inserted next to the abutment die 37the faces 41 and 26 will abut and can be cemented to gether. The generalshape of insert 39 is optional but can best be a circular cross-sectionpiece which is temporarily held relative to crown or coping 38 by wax orcemented to the coping if the coping is made of plastic. The technicianthen adds inlay wax 42 to the crown 38, building up the thickness of wax42 sufficiently so that the metal frame which will ultimately berepresented by the wax is thick and strong enough to make a good supportfor the porcelain which is ultimately applied to the exterior of themetal. The configuration of the wax 42 after it is fully applied issmaller than the ultimate porcelainized crown which will fit onto theabutment tooth. In other words, the exterior of the wax 42 is onlysufficient to represent the exterior of the metal portion of theabutment of the restoration. The abutment die 37 is similar to any otherrestoration abutment die except for the use of the insert 39 having theflat face 41. In FIG. 5 there are abutments on either side, the one onthe left showing-in dotted lines the ultimate shape of the wax and theone on the right showing the wax applied.

The technician then applies carding wax 47 to the tissue area 46 of themodel 36, the wax being about 1 to 2 mm thick. If the metal of therestoration is to be tissue bearing, then excess wax is trimmed away andthe wax 47 lifted off the model with the core. If the metal of therestoration is to be porcelainized at the tissue area, the

wax 47 is left behind on the model. The technician then selects pontics21 constructed in accordance with this invention of the proper generalshape and size as has heretofore been explained. These pontics are thenstuck in place on the carding wax47, the left-hand pontic 21 being closeto the abutment die 37 with the surface 26 of the pontic and the surface41 of the abutment in close proximity. The other pontics are similarlyplaced, the right-hand pontic 21 having the same relationship to theright-hand abutment die 37 as on the left-hand side. The pontics 21stick to the wax 47 sufficiently to enable the technician to check thearticulation of the die by inserting in the original model and theninserting the models of the two jaws in an articulator and making surethat the bite is proper. Any adjustments that are necessary areperformed as the type of wax 47 remains pliable and also serves as amatrix or index.

After the articulation is as desired, the technician starts with theleft-hand pontic 21 (or the right-hand pontic if desired), removingitfrom the wax 47, placing a drop of cement such as lucite and acetonecement on surface 26 and replacing the pontic 21 so that the cement 49causes the adjoining surfaces 41 and 26 to permanently stick together.After the cement 49 has hardened, the next pontic 21 is removed from thewax 47, cement applied to its left surface 26 and the pontic is thenreplaced on the wax so that the surfaces 26 of the two pontics arecemented together. This operation is repeated until the right-handpontic 21 is cemented to the insert 39 of the right-hand abutment die37.

After all of the ponticshave been cemented in place, the cap 31 of eachpontic 21 isremoved. Removal of the caps is facilitated by reason oftheir flexibility and the fact that they are of a materialwhich does notreadily adhere to the cement 49. The completion of this operation isshown in FIG. 8 where the dotted lines represent the outlines of theoriginal caps. Sprueforming material 51 is then waxed on to the cores 22as well as to the wax 42 of each abutment 37.

An investment is then made from the model and this is shown in FIG. 9wherein there is a cavity 53 formed in the investment material 52 whichrepresents the core 22 of the pontic. There are sprues 54 for the propercasting and venting of the ultimate metal casting which correspond tothe sprues 51 and are all in accordance with conventional practice. Withrespect to the abutment, there is a hollow 40 which represents the coreor abutment die 38 and a cavity 58 which is filled with wax or plasticand represents a crown or coping which was molded over the abutment die.The section 40 remains in the investment to provide the cavity 58 whichis later to be filled with metal.

A metal casting of gold or other suitable material is made from theinvestment mold of FIG. 9, and this is shown in FIG. 10. The metal ofthe sprues 57 is cut away and discarded. There is thus formed a metalframe 51 having exposed connecting portion 62 joining one tooth to theother, and this is preferably on the lingual side of the restoration.There is a plurality of metal teeth 63 each slightly reduced as comparedwith the eventual tooth of the restoration.

In accordance with conventional practice, porcelain 66 is applied to themetal frame 61 concealing the metal teeth 63 in all areas except theexposed connecting portion 62. The abutment crowns or copings 37b arehollow, the hollows corresponding in shape to'the abutment teeth whichhave been left by the dentist in the mouth of the patient. in applyingthe porcelain 66, the porcelain technician uses approximately the samethickness as the wall thickness of the cap 31 of the pontics 21.

FIG. 13 is a modification of the structure of FIG. 2 and many of theelements are substantially the same as in FlG. 2. Those elementsappearing in the lower jaw are indicated by the same reference numeralsas in FIG. 2 followed by the subscript b and those in the upperjaw aredesignated by the same reference numerals followed by subscript c. Thepontic 21b has a core 22b similar to that of FIG. 2. However, the cap31b is formed with a top 71 having a plurality of lateral locatinggrooves 72. This form of top 71 is less expensive to mold than thatshown in FIGS. 1 and 2; and furthermore, the same mold may be used foruppers and lowers; and generally speaking, the same mold may be used fora plurality of different bicuspids and molars. The upper die, whichmatches the lower die, may be made from the impression of the actualteeth of the patient. However, in FlG. 13 the pontic 21c is provided toindicate that there is a restoration of the upper and the lower jaws.Core 220 is similar to core 22b and the top face 71c is similar to face71 and the grooves 72c are similar to grooves 72. The grooves 72, 720are fit together in an articulation machine to provide the proper bitefor the patients mouth. This may be varied by interfitting differentgrooves 72 with different grooves 72c. In other words, the pontic 21cmay be moved to the left or right as viewed in FIG. 13 to accomplish theproper articulation. The same left or right movement may be accomplishedwhere the pontic 710 is replaced by a die that actually conforms to thenatural tooth of the patient.

In other respects the pontics 71b and c resemble those of precedingmodifications and the same reference numerals followed by subscripts band c are used to designate corresponding parts.

lt is sometimes desirable to completely cover with porcellain the metalframe of abutment copings and adentulous pontics. This construction isalso possible using the present invention.

Directing attention to FIGS. 14 and 15, extension 23 is eliminated fromthe core of pontic 21d. The lateral extensions 24 with their opposedflat faces 26d are used (as in FIGS. 1 and 2). Directing attention toFIGS. 16 and 17, only the interproximallateral extensions 24e havingflat faces 26c are used and the lingual extension 23a of FIGS. 3 and 4is eliminated. in other respects, the structures of FIGS. 14-15 andFlGS. 16-17 resemble those of FIGS. 1-2 and 3-4 and the same'referencenumerals followed by subscripts d and e respectively are used todesignate corresponding parts.

What is claimed is:

1. A pontic for dental restorations comprising a substantially rigidcore shaped substantially the same as the metal portion of therestoration to be formed and having on either side an inter-proximallateral extension terminating in a face shaped for joining to acooperating face of an adjacent pontic and a flexible plastic capfitting over said core and formed of a material such that said cap canbe detached from said core, said cap having an external configurationsubstantially the same as the porcelainized portion of the restorationto be formed, said cap having lower edges fitting against the top ofsaid lateral extensions.

2. A pontic according to claim 1 in which said core is formed with alingual extension at the tissue line merging with the lateral extensionsat either side of said core. 1

3. A method of forming a pattern for the investment mold of a dentalrestoration comprising forming a model from a portion of the impressionmade of a patients jaw wherein there is at least one abutment reductiondie, affixing to said die a laterally extending insert having an insertface, applying inlay wax to said abutment die to simulate the.exteriorconfiguration of the metal of the crown to be applied to the abutmentreduction of the patients tooth, applying at least one pontic of thetype defined in claim 1 to said model with one of the faces of saidpontic abutting said insert face,

checking the articulation of the assembly of model, wax I and pontic,and removing the cap from said pontic.

4. A method according to claim 3 which further comprises applying secondwax to said model at the situs of said pontic prior to the step ofapplying the pontic and in which said step of applying said ponticinitially comprises temporarily sticking said pontic to said second waxand which further comprises the step of cementing said one face of saidpontic to said insert face after said step of checking the articulationof the assembly.

5. A method according to claim 3 which further comprises applying sprueforming material to said assembly.

6. A method according to claim 5 which further comprises applyinginvestment material around said assembly and hardening said investmentmaterial to form an investment mold.

1. A pontic for dental restorations comprising a substantially rigidcore shaped substantially the same as the metal portion of therestoration to be formed and having on either side an interproximallateral extension terminating in a face shaped for joining to acooperating face of an adjacent pontic and a flexible plastic capfitting over said core and formed of a material such that said cap canbe detached from said core, said cap having an external configurationsubstantially the same as the porcelainized portion of the restorationto be formed, said cap having lower edges fitting against the top ofsaid lateral extensions.
 2. A pontic according to claim 1 in which saidcore is formed with a lingual extension at the tissue line merging withthe lateral extensions at either side of said core.
 3. A method offorming a pattern for the investment mold of a dental restorationcomprising forming a model from a portion of the impression made of apatient''s jaw wherein there is at least one abutment reduction die,affixing to said die a laterally extending insert having an insert face,applying inlay wax to said abutment die to simulate the exteriorconfiguration of the metal of the crown to be applied to the abutmentreduction of the patient''s tooth, applying at least one pontic of thEtype defined in claim 1 to said model with one of the faces of saidpontic abutting said insert face, checking the articulation of theassembly of model, wax and pontic, and removing the cap from saidpontic.
 4. A method according to claim 3 which further comprisesapplying second wax to said model at the situs of said pontic prior tothe step of applying the pontic and in which said step of applying saidpontic initially comprises temporarily sticking said pontic to saidsecond wax and which further comprises the step of cementing said oneface of said pontic to said insert face after said step of checking thearticulation of the assembly.
 5. A method according to claim 3 whichfurther comprises applying sprue forming material to said assembly.
 6. Amethod according to claim 5 which further comprises applying investmentmaterial around said assembly and hardening said investment material toform an investment mold.